Modulation plays an important role in a communications system in converting original data (bits) to an air interface signal that is appropriate for transmission, and is an important part in effective working of the communications system. A modulation mode with a fixed quantity of bits or the like is used for standardization of transmission in a conventional communications system. However, for an existing Long Term Evolution system or the like, a combination of coding and modulation is usually used to implement continuous rate adjustment. For example, different orders of a modulation and coding scheme are defined.
For a future 5th Generation (5G) communications system, application space of a conventional modulation and coding scheme is to be increasingly limited, which is mainly reflected in: With further development of a multimedia application, a dynamic compression ratio of information bits is to become increasingly high. In this background, source coding and channel coding need to be comprehensively considered to effectively reduce channel fading. However, the conventional modulation and coding scheme generally depends on coding with a fixed rate (that is, a mother code rate), effective joint source and channel coding cannot be implemented. Further development of a coding mode (such as a fountain code) with no fixed rate requires a more flexible modulation mode, which can satisfy a modulation demand for any rate. Wide application of a new communications mode such as machine type communications or in-vehicle communications imposes a new requirement on a modulation rate range, modulation reliability, and the like.
A conventional signal modulation mechanism is relatively poor in an aspect such as transmission reliability. Therefore, driven by the current new requirement, researching some signal modulation mechanisms better in transmission reliability and other aspects has great technical significance.